This invention is directed to an improved process for applying a low VOC (volatile organic content) solvent based clear coating composition over a waterborne base coating to form a clear coat/basecoat finish of automotive quality and appearance.
Waterborne coating compositions useful for basecoats for automotive applications are shown in Den Hartog et al U.S. Pat. No. 4,954,559 issued Sep. 4, 1990. The application of a clear coat to a basecoat in a "wet on wet" application is shown in Kurauchi et al U.S. Pat. No. 4,728,543 issued Mar. 1, 1988 and Benefiel et al U.S. Pat. No. 3,639,147 issued Feb. 1, 1972. However, none of the compositions or processes shown in the art form a clear coat/basecoat finish wherein the clear coat is formed from a solvent based composition and the color coat is formed from a waterborne composition and wherein the finish has properties that are required for exterior finishes of automobiles and trucks and the compositions meet desired standards of overall low solvent emissions.
One problem in particular that has been encountered with clear coat/basecoat finishes is the degradation and delamination of the clear coat from a waterborne basecoat upon weathering. Moisture penetration of the clear coat is believed to cause at least a part of the aforementioned problem. The novel process of this invention which uses a particular clear coat forms a clear coat/basecoat finish of automotive quality that is weatherable and durable and the process meets current standards of solvent emissions.